7. Those metro areas are still large, almost all are growing --here's some data to counter your claims

Detroit, Cleveland, PA's large Metro areas (which include Camden, in the Philly Metro Area), and Newark, which is part of the New York City Metro area:

Since 1950:
the Detroit Metropolitan area population has grown 42%
the Cleveland Metropolitan area population has grown 29%
the Pittsburgh Metropolitan area population actually has declined by 9%
the Philadelphia Metropolitan area population has grown 61%
the New York City Metropolitan area population has grown 58%

Since 1980:
the Detroit Metropolitan area population has declined by 2%
the Cleveland Metropolitan area population has declined by 2%
the Pittsburgh Metropolitan area population has declined by 11%
the Philadelphia Metropolitan area population has grown 26%
the New York City Metropolitan area population has grown 30%

In other words, despite you saying these "metro" areas are no more, the Metropolitan areas that include the cities that you listed have mostly all grown since 1950, have mostly grown or slightly declined since 1980, AND, importantly, are still really large Metropolitan areas now.

Metropolitan Statistical Area Population estimate for 2011:
Detroit 4.285 million
Cleveland 2.871 million
Pittsburgh 2.359 million
Philadelphia 6.562 million
New York City 22.214 million